1. Field of the Invention
The present invention relates to a liquid discharge head to discharge a liquid by generating a bubble by acting a thermal energy to the liquid, a liquid discharge method using the liquid discharge head, a recovery method, a liquid discharge apparatus, and a fluid structure body.
The present invention is applicable to an apparatus such as a printer to carry out recording to a recording medium such as a paper, thread, fiber, fabric, leather, metal, plastic, glass, wood, and ceramic, copier, facsimile having a communication system, and word processor having a printer part and an industrial recording apparatus in composite combination with various processing apparatus.
For reference, xe2x80x9crecordingxe2x80x9d in the present invention means not only attaching an image such as a character and a figure having a meaning to the recording medium, but also attaching the image such as a pattern without any meaning.
2. Related Background Art
Conventionally, in a recording apparatus such as printer, an ink jet recording method, namely, so-called bubble jet recording method, in which such energy as heat is applied to a liquid ink in a flow path to generate the bubble and the ink is discharged from a discharge port by an action force caused by an acute volume change according to generation of the bubble to form the image by attaching this to the recording medium, has been known. In the recording apparatus using the bubble jet recording method, as disclosed in U.S. Pat. No. 4,723,129, the discharge port to discharge the ink, the flow path communicating with the discharge port, and an electrothermal converting element as energy generating means to discharge the ink flown in the flow path is generally arranged.
According to such recording method, a high quality image can be recorded in a high speed and with a low noise and also in the head to do this recording method, the discharge port to discharge the ink can be arranged in a high density and thus, there are many advantageous points in which a small apparatus can easily yield the recorded image of a high resolution and a color image. Therefore, the bubble jet recording method is recently applied to many office instruments such as printer, copier, and facsimile and besides, applied to the industrial systems such as textile printing apparatus.
As described above, as the bubble jet technology is increasingly applied to products of many fields, various kinds of requirements have increased. For example, in order to obtain the high quality image, a driving condition was proposed to present the liquid discharge method capable of better ink discharge with a high speed ink discharge and a stable bubble generation and in view of high speed recording, an improved shape of flow path was proposed to realize the liquid discharge head with the high speed to refill the discharged liquid in the liquid flow path.
Among them, in the head to generate the bubble in a nozzle to discharge the liquid according to growth of the bubble, bubble growth toward an opposite direction of the discharge port and a liquid flow caused thereby have been known as factors to lower a discharge energy efficiency and a refilling characteristic. An invention of a structure to improve such discharge energy efficiency and refilling characteristic was proposed in European Patent Application Laid-Open No. EP0436047A1.
In the invention described in the publication, a first valve put between an area around the discharge port and a bubble generating part to shut these and a second valve put between the bubble generating part and an ink supply part to shut these completely are alternately opened and closed (FIG. 4 to FIG. 9 of EP436047A1). For example, in FIG. 7 of the publication, as shown in FIG. 133, a heat generating body 110 is installed in almost center of the ink flow path 112 between an ink vessel 116 on a substrate 125 forming an internal wall of the ink flow path 112 and a nozzle 115. The heat generating body 110 is located in a section 120, of which circumference is all closed, inside the ink flow path 112. The ink flow path 112 is configured by the substrate 125, thin films 123 and 126, directly layered on the substrate 125, and tongue piece 113 and 130 as closing bodies. Tongue piece released are shown by a broken line in FIG. 133. Another thin film 123 extending in a plane parallel to the substrate 125 and ending at a stopper 124 covers over the ink flow path 112. When the bubble occurs in the ink, a free end of the tongue piece 130, in the area of the nozzle, closely contacting with the stopper 126 in a static status is displaced upward and an ink liquid is ejected from the section 120 to the ink flow path 112 subsequently through the nozzle 115. Here, the tongue piece 113 installed in the area of the ink vessel 116 closely contacts with the stopper 124 in the static status and thus, the ink liquid in the section 120 does not go to an ink layer 116. When the bubble in the ink disappears, the tongue piece 130 is displaced downward to contact closely again with the stopper 126. And, the tongue piece 113 falls down in the section 120 and hence, the ink liquid flows in the section 120.
However, in the invention described in EP436047A1, three chambers of the area around the discharge port, the bubble generating part, and the ink supply part are divided in two parts and therefore, in discharge, the ink following a liquid droplet largely tails resulting in a considerable amount of a satellite dots in comparison with a normal discharge system, in which growing, shrinking, and disappearing of a bubble take place (it is presumed that an effect of retreat of a meniscus caused by disappearance of the bubble cannot be employed). On the other hand, a valve in the discharge port side for the bubble causes a great loss of discharge energy. In addition, in replenishment (refilling the ink in the nozzle), the liquid is supplied to the bubble generating part in accordance with disappearance of the bubble. However, the liquid cannot be supplied to the area around the discharge port until the next bubbling occurs and hence, not only a size variation of the liquid droplets discharged is large, but also a frequency responding to discharge is very high and therefore it is not practical.
The present invention proposes the invention to improve a suppressing efficiency of a component to grow a bubble toward a direction opposite to the discharge port and also, on the contrary thereto, improve a discharge efficiency on the basis of a new idea to find out an innovative method and head constitution to realize a high efficiency of the refilling characteristic.
The present inventors, as a result of an intensive research, found that in a nozzle structure of the liquid discharge head, by which a bubble is generated in the nozzle formed linearly and the liquid is discharged according to growth of the bubble, a function of a special check valve allows suppressing bubble growth in the direction opposite (backward) to the discharge port and an effective use of the backward discharge energy for the discharge port side. Furthermore, the present inventors also found that the function of the special check valve allows suppressing a backward bubble growth component and realizing an effective refilling characteristic to make the frequency responding to discharge very high.
Consequently, an object of the present invention is to realize both improvement of a discharge power and improvement of discharge frequency by the nozzle structure and the discharge method using a new valve function and to establish a new discharge system (structure) to achieve the head of the high speed and high image quality of a level, which has not been achieved so far.
To achieve the above described object, the liquid discharge head according to the present invention is characterized by having a plurality of discharge ports to discharge a liquid, a plurality of liquid flow paths, in which an end part is permanently communicated with the respective discharge ports, having a bubble generating area to generate a bubble in the liquid, bubble generating means to generate energy to generate and grow the above described bubble, a plurality of liquid supply port arranged in the plurality of liquid flow paths and communicated with a common liquid supply chamber, and a movable member, having a free end, supported with a very small gap by at least part of the above described liquid flow path side of the above described liquid supply port, and at least the free end part of the above described movable member and an area surrounded by both side parts continuing thereto becomes larger than an opening area prepared in the liquid flow path of the above described liquid supply port, wherein in a status of the above described movable member at rest, the part of the above described discharge port side of the above described movable member contacts with a member for forming the above described liquid supply port and a very small gap is placed between the part of a fulcrum side of the above described movable member and the above described liquid supply port.
Additionally, in the status of the above described movable member at rest, the part of the above described discharge port side of the above described movable member may contact with the member for forming the above described liquid supply port and the very small gap may be placed between a side part in the part of a fulcrum side of the above described movable member and the member to form the above described liquid supply port.
Further, in the status of the above described movable member at rest, the part of the above described discharge port side of the above described movable member may press the member for forming the above described liquid supply port to curve elastically convexly the above described movable member toward the above described liquid supply port side.
According to the above described invention, in the liquid discharge head disposing the movable member by generating the bubble in the bubble generating area by the bubble generating means and discharge the liquid from the discharge port after the liquid flow path is closed almost tightly by closing almost the liquid supply port of the liquid flow path with the movable member, in the status in which the movable member at rest, by contacting the part of the discharge port of the movable member to the member to form the liquid supply port, the time after the bubble generated until the liquid flow path except the discharge port becomes the almost tightly closing status is shortened to suppress movement of the liquid from the liquid flow path to the liquid supply port to a maximum limit. By this, in discharge action, a loss of a discharge power caused by movement of the liquid from the liquid flow path to the liquid supply port reduces to improve discharge efficiency of the liquid discharge head. In addition, together with this, quick transition from the isotropic growth of the bubble to the partial growing and the partial shrinking period, while the part, of the bubble, in the discharge port side grows and the part, of the bubble, in the liquid supply port side shrinks, becomes possible. Further, in the standing status in which the movable member at rest, there is the small gap between the part of the fulcrum side of the movable member and the liquid supply port and there is the very small gap between the side part in the part of the fulcrum side of the movable member and the member to form the liquid supply port and thus, in the status in which the movable member at rest, the liquid supply port communicates with the liquid flow path through the small gap. By this, even in the case where the movable member at rest before a meniscus in the discharge port completely is recovered by the discharge action and the movable member at rest through overshoot in refilling the liquid in the liquid flow path in the status in which the meniscus projects from the discharge port, the liquid moves through the very small gap between the fulcrum side of the movable member and the liquid supply port to make displacement of the meniscus to an appropriate position possible.
In the status of the movable member at rest, the part of the discharge port side of the movable member presses the member to form the liquid supply port to curve elastically and convexly the movable member toward the liquid supply port and thus, when a heat generating body causes membrane boiling to grow the bubble isotropically, by further curving of the movable member convexly to the liquid supply port side, the liquid supply port is closed by the movable member to make the liquid flow path except the discharge port to the substantially tightly closed status. At this time, the movable member curves elastically and convexly toward the an upstream before the bubble grows in maximum size and then, an inconstant heating characteristic of the heat generating body and an inconstant bubbling status, which are caused by an ambient temperature change, are canceled by curving of the movable member. As a result, an inconstant bubbling status caused by the heat generating body and inconstant discharge caused by the ambient temperature change is suppressed. In addition, in this case, the movable member displaces downward in a high order vibration mode and therefore, downward displacement of the free end of the movable member is large and the movable member opens quicker and close quicker and hence, refilling time can be shortened.
Furthermore, the liquid discharge head of the present invention is characterized by having the discharge port to discharge the liquid, the liquid flow path, in which the one end is permanently communicated with the discharge port, having the bubble generating area to generate the bubble in the liquid, the liquid supply port opened in the above described liquid flow path to communicate the liquid supply chamber to hold the liquid supplied to the above described liquid flow path and the above described liquid flow path, and the movable member arranged oppositely to the above described liquid supply port through the gap in the above described liquid flow path, supported making one end of one liquid flow path as the free end, and at least the free end and the area surrounded by both side parts continuing thereto becomes larger than the opening area prepared in the above described liquid flow path of the above described liquid supply port, wherein in the free end of the above described movable member, the flow path passing from the above described liquid supply port formed by the gap to the above described liquid flow path bends.
Such bent flow path can be yielded by having a projected part in a position oppositely located to the free end of the movable member through the gap. Besides, the discharge port and the bubble generating area are in a linear communication status.
The liquid discharge head of the present invention is characterized by having the discharge port to discharge the liquid, the liquid flow path, in which the one end is permanently communicated with the above described discharge port, having the bubble generating area to generate the bubble in the liquid, the liquid supply port opened in the above described liquid flow path to communicate the liquid supply chamber to hold the liquid supplied to the above described liquid flow path and the liquid flow path, and the movable member arranged oppositely to the above described liquid supply port through the gap in the above described liquid flow path, supported making one end of the above described liquid flow path as the free end, and at least the above described free end and the area surrounded by both side parts continuing thereto becomes larger than the opening area prepared in the above described liquid flow path of the above described liquid supply port, wherein the above described liquid flow path has a projected part in the position oppositely located to the above described free end of the above described movable member through the gap.
Furthermore, the liquid discharge head according to the present invention preferably is that the liquid supply port is substantially shut by the above described movable member during a period, while a whole of the bubble generated in the bubble generating area grows isotropically, and during subsequent period, while the part, of the bubble, in the discharge port side grows and the part in the movable member side shrinks, the movable member displaces to the bubble generating area to allow liquid supply from the liquid supply chamber to the liquid flow path through the liquid supply port, or the free end of the movable member in an early period of the bubble displaces to the liquid supply port to shut substantially the liquid supply port toward the liquid flow path, and together with disappearance of the bubble, the free end of the movable member displaces toward the bubble generating area to allow liquid supply from the liquid supply chamber to the liquid flow path through the liquid supply port, or from application of a driving voltage to the bubble generating area until the period, while whole of bubble is isotropically grown by the bubble generating means, is terminated, the movable member closes tightly the liquid supply port to shut substantially and the movable member closes the opening area is closed tightly to shut substantially, and thereafter, during the part, of bubble generated by the bubble generating means, in the discharge port side part grows, the movable member starts to displace from the position, in which the opening area is closed tightly to shut substantially, to the above described bubble generating means side to make liquid supply from the common liquid supply chamber to the above described liquid flow path possible. By this, in the free end of the movable member, the flow path from the liquid supply port to the liquid flow path bends and thus, the flow of the liquid from the liquid flow path to the liquid supply port in the early period of bubbling is suppressed. By this, the substantially tightly closed situation of the liquid flow path and the liquid supply port is reliably created and hence, discharge characteristics are more improved. In addition, by suppressing the flow of the liquid from the liquid flow path to the liquid supply port in the early period of bubbling, a retreat distance of the meniscus in the discharge port after a droplet is discharged can be minimized. As the result, after discharge, the time for recovery of the meniscus to the initial status is very quick. In other words, the time, in which ink replenishment (refilling) of a predetermined volume in the liquid flow path is completed, is short and therefore, in practicing ink discharge of a high accuracy, (a predetermined volume) a discharge frequency (driving frequency) can be greatly improved.
Furthermore, the liquid discharge apparatus of the present invention has any one of the above described liquid discharge heads according to the present invention, and carrying means to carry the recording medium to receive the liquid discharged from the liquid discharge head.
Specifically, the above described liquid discharge apparatus operates recording by discharging the ink from the above described liquid discharge head to attach the ink to the above described recording medium.
According to the above described liquid discharge apparatus, recording can be operated by equipping with the above described liquid discharge head to increase the discharge efficiency of the liquid and suppress inconstant discharge volume.
According to the above described configuration, when the bubble occurs in the bubble generating area, the liquid flow path and immediately in the early period thereof, the liquid supply port are substantially tightly closed by the movable member. Therefore, a pressure wave generated by growth of the bubble in the bubble generating area is not propagated to the liquid supply port side and the liquid supply chamber side, but a large part thereof is directed to the discharge port and thus, a discharge power is greatly improved. In the case where a high viscosity recording liquid is used to fix the ink to a recording paper in a high speed and prevent smearing in a boundary between black and color areas, the great improvement of the discharge power allows better discharge. In addition, under an environmental change in recording, particularly in a low temperature and a low humidity environment, the following case may occur: the area, in which the ink increases viscosity, spreads in the discharge port to disturb normal ink discharge on use, however, in the present invention, even a first occasion of discharge is no problem. The discharge power has been greatly increased and therefore, energy consumed for discharge can be reduced by reducing the size of the heat generating body used for the bubble generating means.
The bubble in the bubble growing area is largely grown toward the discharge port side and suppressed to grow toward the liquid supply port side. Thus, by locating a disappearing point in the part from near a center of the bubble generating area to the discharge port side and keeping a bubbling power, the bubble disappearing power can be reduced. Therefore, a life of the heat generating body influenced by a mechanical and physical break caused by the bubble disappearing power of the bubble generating area can be greatly prolonged.
Other configuration and effect of the present invention will be understood on the basis of a description of each embodiment.
For reference, xe2x80x9cupstreamxe2x80x9d and xe2x80x9cdownstreamxe2x80x9d used in description of the present invention are used as expressions concerning the direction of the flow from the supply source of the liquid to the discharge port through the bubble generating area (or, the movable member) or the direction in this configuration.
The xe2x80x9cdownstream sidexe2x80x9d related to the bubble itself means the downstream side related to the direction in the above described flow direction to the center of the bubble and the above described configuration, or the bubble generated in the area of the downstream than the center of the area of the heat generating body.